Pellicle frame and pellicle

ABSTRACT

The present invention is to provide a pellicle frame in a frame shape, having an upper end face to arrange a pellicle film thereon and a lower end face to face a photomask, and which is characterized by being provided with a notched part from an outer side face toward an inner side face of the upper end face, and to provide a pellicle characterized by including the pellicle frame as a component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of application Ser. No.16/735,116, filed on Jan. 6, 2020, now U.S. Pat. No. 11,237,476, whichclaims the benefit under 35 U.S.C. § 119(a) to Patent Application No.2019-016992, filed in Japan on Feb. 1, 2019, all of which are herebyexpressly incorporated by reference into the present application.

TECHNICAL FIELD

The present invention relates to a pellicle frame to be attached onto aphotomask for is lithography as a dust guard, and to a pellicle.

BACKGROUND ART

In recent years, in a design rule of a large scale integration (LSI),miniaturization to sub-quarter micron has progressed, and along with theminiaturization, the wavelength of an exposure light source has beenshortened. That is, the exposing light source has shifted from a g-line(436 nm) or i-line (365 nm) by a mercury lamp to a KrF excimer laser(248 mm), ArF excimer laser (193 nm) or the like, and further, extremeultra violet (EUV) exposure using an EUV light having a main wavelengthof 13.5 nm has been also studied.

In the semiconductor production of a LSI, a very large scale integration(VLSI) or the like, or in the production of a liquid crystal displayboard, a pattern is formed by irradiating a semiconductor wafer or anoriginal plate for liquid crystal with light, however, if dust adheresto a photomask for lithography and a reticle (hereinafter, collectivelyreferred to as an “exposure original plate”), which are to be used inthis case, this dust absorbs light or bends light, so that there hasbeen a problem that the transferred pattern is deformed or the edgebecomes coarse, further the base becomes black and dirty, and thedimension, the quality, the appearance, or the like is impaired.

These works are usually performed in a clean room, however, it is stilldifficult to keep an exposure original plate clean. Accordingly, amethod in which exposure is performed after attaching a pellicle as adust guard onto a surface of an exposure original plate is generallyadopted. In this case, foreign matters do not adhere directly onto asurface of an exposure original plate but adhere to a pellicle,therefore, if the focal point is set on a pattern of the exposureoriginal plate at the time of lithography, the foreign matters on thepellicle become irrelevant to the transfer.

In the basic constitution of the pellicle, a pellicle film having a hightransmittance for the light to be used for exposure is stretched on anupper end face of a pellicle frame, and further an airtight gasket isformed on a lower end face of the pellicle frame. As the airtightgasket, in general, a pressure-sensitive adhesive layer is used. Thepellicle film is made of nitrocellulose, cellulose acetate, afluorine-based polymer or the like, which well transmits the light (ag-line (436 nm) or i-line (365 nm) by a mercury lamp, a KrF excimerlaser (248 nm), ArF excimer laser (193 nm) or the like) to be used forexposure, however, for EUV exposure, an ultrathin silicon film or acarbon film has been studied as a pellicle film.

There are some restrictions on a pellicle frame for EUV exposure as amatter of convenience of an exposure device. Since the pelliclearrangement space in an EUV exposure device is small, the height of apellicle is required to be 2.5 mm or less.

In addition, since EUV exposure is performed under a high vacuum, apellicle for EUV is required to withstand the pressure changes from anatmospheric pressure to a vacuum, and a ventilation part of the EUVpellicle is required to have a large area. In view of this, in PatentDocuments 2 and 3, a pellicle frame with a filter, with which a wideventilation area can be obtained, has been proposed. Since the height ofa pellicle is low, it is preferred to provide a filter so as to beparallel to a film in order to attach the filter, and in a case where afilter is provided on an upper end face or a lower end face of apellicle frame, a curved part is generated in a ventilation passage. Ifthere is a curved part in a ventilation passage, particularly when thepressure is returned from a high vacuum to an atmospheric pressure, alarge resistance is generated in the ventilation passage, and a pressuredifference between the inside and outside of the pellicle is generated,as a result of which there has been a concern that a damage to thepellicle film may be caused. There is no problem in a case of slowlyreturning the pressure, and from the viewpoint of the workability, ithas been found that there is a case where it may be required to returnthe pressure more quickly from a high vacuum to an atmospheric pressure.Further, when a pellicle frame is cleaned, it is difficult tosufficiently clean the ventilation passage having a curved part, andthere has been a concern that foreign matters remain.

In Patent Document 4, a pellicle mechanically fixed to a mask with aholding spring provided on the pellicle and a fastener called a studprovided on the mask has been proposed. In that pellicle, a gap of 200to 300 μm is created between the mask and the pellicle to perform theventilation, and therefore the ventilation ability is sufficient,however, if the pellicle is mechanically fixed, contact between metalsis necessarily generated at the connection part. If the contact betweenmetals is generated, there is a concern that dust generation may becaused.

In the specification of Japanese Patent Application No. 2017-197004filed previously by the applicant of the present application, a pellicleframe having a large number of through holes on the side face has beenproposed. However, in such a pellicle frame, in order to provide aventilation part having a large area with only the through holes, it isrequired to open an extremely large number of through holes, and inparticular, if a pellicle frame is made of a material that is easilydamaged, the processing is difficult, and requires a high cost. Further,in a case where foreign matters remained in the through holes due toinsufficient cleaning, since the visual inspection cannot be performedin the through holes, it has been found that it is difficult to find theforeign matters inside the through holes.

In addition, in the specification of Japanese Patent Application No.2017-19682 filed previously by the applicant of the present application,a pellicle frame in which a notched part is provided on a lower end faceas a holding part of a peeling jig and further a ventilation part hasbeen proposed. In such a pellicle frame, the ventilation ability and theprocessability are sufficient, however, there is a drawback that abonded part between the pellicle frame and a mask is reduced. Because ofthe small bonded part, there is a concern that the pellicle frame may bedropped if the pellicle is used over a long period of time. In order toprevent the dropping of a pellicle, it is conceivable to use apressure-sensitive adhesive having a strong adhesive force, however, thepellicle needs to be peeled off from the mask after the use or when afailure occurs in the pellicle. If the adhesive force is extremelystrong, a strong force is applied to the pellicle when the pellicle ispeeled off, and a possibility that the pellicle film is damaged isextremely high. If the pellicle film is damaged, the mask iscontaminated, and therefore, it is difficult to use a pressure-sensitiveadhesive having a strong adhesive force.

CITATION LIST

-   Patent Document 1: JP-A 2016-200616-   Patent Document 2: JP-A 2017-83791-   Patent Document 3: JP-A 2016-191902-   Patent Document 4: WO 2016/124536

SUMMARY OF THE INVENTION

The present invention has been made in view of such a circumstancedescribed above, and an object of the present invention is to provide: apellicle frame with which when EUV exposure is performed under a highvacuum, the pellicle film withstands the pressure changes from anatmospheric pressure to a vacuum, and is not damaged, a large number ofthrough holes are not required to be arranged, it is not difficult tofind foreign matters, the pellicle film is not damaged even if anadhesive agent or pressure-sensitive adhesive having strong adhesiveforce is used, and a possibility that the pellicle film is peeled off isextremely low even if the pellicle frame is used over a long period oftime, and a pellicle using the pellicle frame.

The present inventor has found a pellicle frame in a frame shape, havingan upper end face to arrange a pellicle film thereon and a lower endface to face a photomask, with which by providing a notched part fromthe outer side face toward the inner side face of the upper end face ofthe pellicle frame, a bonded part between the pellicle frame and apellicle film is reduced, however, since the pellicle film is notrequired to be peeled off from the pellicle frame, an adhesive agent orpressure-sensitive adhesive having strong adhesive force can be used,and further, since the load to be applied to the bonded par is only fromthe pellicle film, a possibility that the pellicle film is peeled off isextremely low even if the pellicle frame is used over a long period oftime, and thus have completed the present invention.

Therefore, the present invention provides the following pellicle frameand pellicle.

1. A pellicle frame in a frame shape, having an upper end face toarrange a pellicle film thereon and a lower end face to face aphotomask, and being provided with at least one notched part from anouter side face toward an inner side face of the upper end face.2. The pellicle frame according to 1 described above, wherein thenotched part is formed from the outer side face up to the inner sideface.3. The pellicle frame according to 1 described above, wherein thepellicle frame has a thickness of less than 2.5 mm, and is made oftitanium.4. The pellicle frame according to 1 described above, wherein thepellicle frame has a thickness of less than 2.5 mm, and is made of asilicon crystal.5. A pellicle, including the pellicle frame according to 1 describedabove as a constituted component.6. The pellicle according to 5 described above, wherein an adhesiveagent is provided on an upper end face excluding the notched part in anupper end face of the pellicle frame.

Advantageous Effects of the Invention

According to the present invention, a pellicle frame that has sufficientventilation ability, favorable pellicle frame processability, andfavorable adhesiveness to a mask, and a pellicle can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an example of the pellicle frameaccording to the present invention;

FIGS. 2A and 2B show another example of the pellicle frame according tothe present invention, FIG. 2A is a plan view as viewed from the upperend face side, and FIG. 2B is a plan view as viewed from the outer faceside of the short side; and

FIG. 3 is a schematic view showing a state that the pellicle accordingto the present invention is attached onto a photomask.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The pellicle frame according to the present invention is a pellicleframe in a frame shape, which has an upper end face on which a pelliclefilm is to be arranged and a lower end face to face a photomask.

As long as the pellicle frame has a frame shape, the shape correspondsto the shape of a photomask onto which a pellicle is to be attached. Ingeneral, the shape of a pellicle frame is a quadrilateral (rectangularor square) frame shape.

In addition, in a pellicle frame, there are a face on which a pelliclefilm is to be arranged (herein, referred to as an upper end face) and aface to face a photomask (herein, referred to as a lower end face) whenthe pellicle frame is attached onto the photomask.

In general, on the upper end face of a pellicle frame, a pellicle filmis arranged with an adhesive agent or the like therebetween, and on thelower end face, a pressure-sensitive adhesive or the like for attachinga pellicle onto a photomask is provided, but cases of the presentinvention are not limited to the above.

The material for a pellicle frame is not limited, and a known materialcan be used. In a pellicle frame for EUV, since there is a possibilityof being exposed to a high temperature, a material having a smallthermal expansion coefficient is preferred. As the material for apellicle frame, Si, SiO₂, SiN, quartz, invar, titanium, a titaniumalloy, or the like can be mentioned. Among them, from the viewpoint ofthe ease of processing or the lightness in weight, titanium, or atitanium alloy is preferably used.

The size of a pellicle frame is not particularly limited, however, sincethe height of a pellicle for EUV is limited to 2.5 mm or less, thethickness of a pellicle frame for EUV is smaller than the height and isless than 2.5 mm.

In addition, the thickness of a pellicle frame for EUV is preferably 1.5mm or less in consideration of the thickness of a pellicle film, a maskpressure-sensitive adhesive and the like.

In the pellicle frame according to the present invention, a notched partis provided from an outer side face toward an inner side face of anupper end face of the pellicle frame. Although there are no restrictionson the position to be provided with the notched part and the number ofthe notched parts, the total area of the opening parts is preferably 20mm² or more, and more preferably 30 mm² or more.

In addition, usually, on a side face of a pellicle frame, a jig holeused for handling or peeling off a pellicle from a photomask isprovided. The size of the jig hole is 0.5 to 1.0 mm in length (diameterin a case of a circle) in a thickness direction of the pellicle frame.The shape of the hole is not limited, and may be a circle or arectangle. Further, usually, the jig hole is a hole that does notpenetrate from an outer side face to an inner side face, and in additionto the jig hole, a vent hole that penetrates from an outer side face toan inner side face may also be provided. In a case of the vent hole,there are no restrictions on the position to be provided with the venthole and the number of the vent holes.

In addition, a filter may be arranged in a notched part formed from anouter side face up to an inner side face of a pellicle frame. In thatcase, a filter may be arranged on either the inner side face or theouter side face of the pellicle frame so as to cover the notched part.

In the pellicle according to the present invention, a pellicle film isarranged on an upper end face of the pellicle frame as described abovewith a pressure-sensitive adhesive or an adhesive agent therebetween.The material for the pressure-sensitive adhesive or the adhesive agentis not limited, and a known material can be used. The pressure-sensitiveadhesive or the adhesive agent is arranged on an upper end faceexcluding the notched parts of the pellicle frame. In order to stronglyhold the pellicle film, a pressure-sensitive adhesive or adhesive agenthaving a strong adhesive force is preferred.

On the material for the pellicle film described above, there are noparticular restrictions, and a material having a high transmittance anda high light resistance, at a wavelength of an exposure light source ispreferred. For example, an ultrathin silicon film, a carbon film, or thelike is used for EUV exposure.

Further, on a lower end face of the pellicle frame, a maskpressure-sensitive adhesive for attaching the pellicle frame onto aphotomask is formed. In general, the mask pressure-sensitive adhesive ispreferably arranged over the entire circumference of the pellicle frame.

As the above-described mask pressure-sensitive adhesive, a knownpressure-sensitive adhesive can be used, and an acrylicpressure-sensitive adhesive or a silicone-based pressure-sensitiveadhesive can be suitably used. The pressure-sensitive adhesive may beprocessed into an arbitrary shape as needed.

Onto a lower end face of the above-described mask pressure-sensitiveadhesive, a release layer (separator) for protecting thepressure-sensitive adhesive may be attached. There are no particularrestrictions on a material for the release layer, and for example,polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE),tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA),polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC),polypropylene (PP), or the like can be used. Further, as needed, arelease agent such as a silicone-based release agent or a fluorine-basedrelease agent may be applied onto a surface of the release layer.

Herein, FIG. 1 shows an example of a pellicle frame 1 according to thepresent invention, and in each drawing, the reference sign 11 shows aninner side face of the pellicle frame, the reference sign 12 shows anouter side face of the pellicle frame, the reference sign 13 shows anupper end face of the pellicle frame, and the reference sign 14 shows alower end face of the pellicle frame. In the upper end face of thepellicle frame 1 of FIG. 1 , notched parts 10 and 10 are provided on theshort sides, respectively, and not provided on the long sides, in theupper end face. In addition, usually, on the long side of the pellicleframe, a jig hole used for peeling off a pellicle from a photomask isprovided, however, the jig hole is not specifically shown in FIG. 1 .

FIGS. 2A and 2B show an example in which in an upper end face of apellicle frame 1, notched parts 10 and 10 are provided on the shortsides in the upper end face, respectively, and further notched parts 10and 10 are provided also on the long sides in the upper end face,respectively, that is, a total of four notched parts are provided in theupper end face. In FIGS. 2A and 2B, the notched parts are each formed bycommunicating from an outer side face up to an inner side face. In FIGS.2A and 28 , the reference sign W shows a width of the notched part, thereference sign D shows a depth of the notched part, and the referencesign T shows a height of the notched part.

FIG. 3 shows a pellicle 20, and a pellicle film 2 is bonded andstretched onto an upper end face of a pellicle frame 1 by an adhesiveagent 4. Further, the pellicle frame 1 is peelably bonded to a photomask3 by a pressure-sensitive adhesive 5 to protect a pattern surface on thephotomask 3.

EXAMPLES

Hereinafter, the present invention is specifically described withreference to Examples and Comparative Examples, however, the presentinvention is not limited to the following Examples.

Example 1

A pellicle frame (with an outer size of 150 mm×118 mm×1.5 mm, and aframe width of 4.0 mm) made of titanium (having a linear expansioncoefficient of 8.4×10⁻⁶ (1/K), and a density of 4.5 g/cm³) was prepared.

In an outer side face of a long side of the pellicle frame, two jigholes each having a diameter of 1 mm and a depth of 1.2 mm were providedat two places each with a distance of 52 mm away from the center of theside to each of the corner directions. A notched part with a width of 90mm, a height of 0.1 mm, and a depth of 4 mm was provided in an upper endface at the center of each of the sides of the pellicle frame. Thenotched part was formed from an outer side face up to an inner sideface.

The pellicle frame was cleaned, and one obtained by adding 1 part byweight of a curing agent (PT-56 manufactured by Shin-Etsu Chemical Co.,Ltd.) into 100 parts by weight of a silicone pressure-sensitive adhesive(X-40-3264 manufactured by Shin-Etsu Chemical Co., Ltd.) and stirringthe mixture was applied on the upper end face excluding the notchedparts of the pellicle frame so as to have a width of 1 mm and athickness of 0.1 mm. Further, as a mask pressure-sensitive adhesive, oneobtained by adding 0.1 part by weight of a curing agent (L-45manufactured by Soken Chemical & Engineering Co., Ltd.) into 100 partsby weight of an acrylic pressure-sensitive adhesive agent (SK-1495manufactured by Soken Chemical & Engineering Co., Ltd.) and stirring themixture was applied over the entire circumference on a lower end face ofthe pellicle frame so as to have a width of 1 mm and a thickness of 0.1mm.

After that, the pellicle frame was heated at 90° C. for 12 hours to curethe pressure-sensitive adhesive on the upper end face and lower end faceof the pellicle frame. Subsequently, an ultrathin silicon film was usedas a pellicle film, and the ultrathin silicon film was press bonded tothe pressure-sensitive adhesive formed on the upper end face of thepellicle frame, and a pellicle was completed.

The pellicle was attached onto a quartz mask with a size of 150 mm×150mm as a substitute for a photomask.

Example 2

A pellicle frame (with an outer size of 150 mm×118 mm×1.5 mm, and aframe width of 4 mm) made of titanium was prepared.

In an outer side face of a long side of the pellicle frame, two jigholes each having a diameter of 1 mm and a depth of 1.2 mm were providedat two places each with a distance of 52 mm away from the center of theside to each of the corner directions. In an upper end face of each ofthe long sides of the pellicle frame, two notched parts each with awidth of 50 mm, a height of 0.1 mm and a depth of 4 mm were provided attwo places with a space of 15 mm. In an upper end face of each of theshort sides of the pellicle frame, two notched parts each with a widthof 40 mm, a height of 0.1 mm and a depth of 4 mm were provided at twoplaces with a space of 15 mm. These notched parts were each formed froman outer side face up to an inner side face.

The pellicle frame was cleaned, and one obtained by adding 1 part byweight of a curing agent (PT-56 manufactured by Shin-Etsu Chemical Co.,Ltd.) into 100 parts by weight of a silicone pressure-sensitive adhesive(X-40-3264 manufactured by Shin-Etsu Chemical Co., Ltd.) and stirringthe mixture was applied on the upper end face excluding the notchedparts of the pellicle frame so as to have a width of 1 mm and athickness of 1 mm. Further, a silicone pressure-sensitive adhesivesimilar to the above pressure-sensitive adhesive was also applied overthe entire circumference on a lower end face of the pellicle frame so asto have a width of 1 mm and a thickness of 1 mm.

After that, the pellicle frame was heated at 90° C. for 12 hours to curethe pressure-sensitive adhesive on the upper end face and lower end faceof the pellicle frame. Subsequently, an ultrathin silicon film was usedas a pellicle film, and the ultrathin silicon film was press bonded tothe pressure-sensitive adhesive formed on the upper end face of thepellicle frame, and a pellicle was completed.

The pellicle was attached onto a quartz mask with a size of 150 mm×150mm as a substitute for a photomask.

Comparative Example 1

A pellicle frame (with an outer size of 150 mm×118 mm×1.5 mm, and aframe width of 4 mm) made of titanium was prepared. Instead of providinga notched part on each side of the pellicle frame, through holes eachhaving a diameter of 0.8 mm were provided at 20 positions on each sideas ventilation parts. The constitution except for the constitutiondescribed above was the same as the constitution of Example 1.

Comparative Example 2

A pellicle frame (with an outer size of 150 mm×118 mm×1.5 mm, and aframe width of 4 mm) made of titanium was prepared. The constitution wasthe same as the constitution of Example 1 except that a notched part wasprovided at the center of each side in the lower end face of thepellicle frame.

The pellicle of each example of Examples 1 and 2 and ComparativeExamples 1 and 2 was subjected to the following attachment stabilitytest, ventilation test, and foreign matter inspection after cleaning.The evaluation results are shown in Table 1.

[Attachment Stability Test]

A pellicle attached to a quartz substrate was placed so that thepellicle was positioned on the lower side, heated to 80° C. in an oven,and left to stand for 1 week, and the presence or absence of thedropping of the pellicle was confirmed. As a result, only the pellicleof Comparative Example 2 was dropped.

[Ventilation Test]

A pellicle attached to a quartz substrate was placed in a vacuum device,and the pressure was reduced to 1E-4 (1.0×10⁻⁴) Pa in 1 minute. Afterthat, the pressure was returned to an atmospheric pressure over 2minutes, and the state of the pellicle film was confirmed. In all of thepellicle films of Examples 1 and 2 and Comparative Examples 1 and 2,abnormality was not confirmed.

[Foreign Matter Inspection after Cleaning]

After cleaning a pellicle frame, adhered foreign matters on a surface ofthe pellicle frame was inspected by using a condensing light under afluorescent lamp and in a dark room, and the adhered foreign matterswere not confirmed in all of the pellicle films of Examples 1 and 2 andComparative Examples 1 and 2.

In Comparative Example 1, since the presence or absence of foreignmatters inside a through hole cannot be confirmed by visual inspection,the presence or absence of foreign matters inside the through hole wasconfirmed by using a microscope after cleaning the pellicle frame. Ofthe 80 through holes, a foreign matter with a size of around 100 μm wasfound in two through holes. Further, since the visual observation wasperformed by using a microscope, many foreign matters adhered to asurface of the pellicle frame due to the use of the microscope.

TABLE 1 Attachment Ventilation Foreign matter Material stabilitycharacteristic inspection Example 1 Titanium ○ ○ ○ Example 2 Titanium ○○ ○ Comparative Titanium ○ ○ x Example 1 Comparative Titanium x ○ ○Example 2

From the above Table 1, in each of the pellicles of Examples 1 and 2, byusing a pellicle frame having a notched part in an upper end part of thepellicle frame, the foreign matter inspection can be more easilyperformed as compared with the pellicles of Comparative Examples 1 and2, and it can be understood that the attachment stability is favorable,and the ventilation ability is sufficient.

Japanese Patent Application No. 2019-016992 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

The invention claimed is:
 1. A pellicle comprising: a pellicle framehaving a frame shape, an upper end face and a lower end face to face aphotomask; and a pellicle film arranged at the upper end face of thepellicle frame, wherein the pellicle frame is provided with at least onerecessed portion from an outer side face toward an inner side face ofthe upper end face, and wherein the recessed portion is a ventilationpart.
 2. The pellicle according to claim 1, wherein the recessed portionis formed from the outer side face up to the inner side face.
 3. Thepellicle according to claim 1, wherein the pellicle frame has athickness of less than 2.5 mm.
 4. The pellicle according to claim 1,wherein an adhesive agent or a pressure-sensitive adhesive is providedon the upper end face of the pellicle frame excluding the recessedportion in the upper end face of the pellicle frame.
 5. The pellicleaccording to claim 1, wherein a curved part is not formed in aventilation passage of the ventilation part.
 6. The pellicle accordingto claim 1, wherein the pellicle is applied to EUV.
 7. An assemblycomprising the pellicle of claim 1 and an exposure original plate,wherein the pellicle is attached to the exposure original plate.
 8. Anexposure method, comprising performing an exposure using the assemblyaccording to claim
 1. 9. A manufacturing method of a semiconductordevice, comprising a step of forming a pattern by irradiating asemiconductor wafer with light wherein the assembly according to claim 7is adopted.
 10. The pellicle according to claim 1, wherein the pelliclefilm is arranged on the upper end face of the pellicle frame.